The present invention relates to recording a code on a key which is used in electronic locks and, more particularly, is concerned with utilizing two Moire fringe pattern film strips and two photodetector and photoemitter pairs to produce a clock signal for periodically generating a recording pulse as a function of actual distance moved by the key over a permanently positioned magnetic head.
There are many devices for recording a code on a key which is used in electronic locks. Typically, the key is inserted into a slot and a magnetic head is moved linearly along the length of the key while the magnetic head records the code on the key.
There are many methods for recording the code on the key. One method uses pulse width modulation while another method records pulses along one track which, represents binary zero (0), and records pulses on another track, which represents binary one (1). The method which uses two tracks representing 0 and 1 is known as the dual track code method.
The code is recorded on a magnetic strip laminated to the key. When the key is fully inserted in the recording device the magnetic head moves across the magnetic strip and records the code. Since the key remains stationary while the magnetic head moves across the magnetic strip, the speed of the magnetic head is important. The accuracy of the magnetic head movement requires a drive motor, motor drive circuitry to control the speed of the motor, means for generating rotary optical pulses to measure the speed of the motor, and many other supporting elements. A recording device which uses movement of the magnetic head to record the code is usually expensive and, due to the many parts required by the device, is complicated and susceptible to many problems such as motor noise, gear backlash and gear noise.
A simpler, lower cost and more efficient recording device would permanently position the magnetic head near the entrance of the slot. When the key is inserted at the entrance of the slot and the key can pass over or under the magnetic head and the magnetic head could record the code as a function of actual distance moved by the key relative to the stationary magnetic head. A device of this type would eliminate many expensive parts and decrease the complexity of the device, thereby decreasing the susceptibility to problems.